Coil devices installed in circuits of various types of AC equipment are configured by winding a coil around a ring-shaped magnetic core.
In order to facilitate the winding operation, a coil device is proposed in which a gap portion is formed by cutting away a part of a toroidal magnetic core, which has a circular ring shape, such that the cut-away part has a certain width in the direction of the magnetic path, and a conducting wire is wound around the core while inserting the conducting wire through the gap portion (see FIG. 10 with respect to the conventional technology in Patent Document 1, for example).
In the above-described coil device, the conducting wire needs to be manually wound around the core on a turn-by-turn basis, and thus, the manufacturing efficiency is low.
To address this issue, a coil device 70 is also proposed that is configured by bending a rod-shaped magnetic core into a substantially circular shape including a rectilinear portion 71 as shown in FIG. 14(a), and forming a gap portion 74 such that one end surface 72 opposes a side surface 73 of the rectilinear portion 71 (see Patent Documents 1 and 2, for example).